When the joint is infected, pus builds up, causing damage to the structures of the joint.

Infection

Entry into the body of microorganisms that can reproduce and cause disease.

Pus

A bodily fluid that is the result of an inflammatory response at an infection site. Its color can range from whitish to yellow to green, depending on the composition. Pus is mainly composed of dead bacteria, white blood cells and cellular debris.

Upper respiratory tract

The nose, sinuses, larynx and trachea parts of the respiratory tract which function to carry air to and from the lungs.

Urinary tract

The organs and tubes involved in transporting urine within the body and out of it.

Risk factors

Factors that can increase the risk of developing septic arthritis include:

Chemotherapy

A medication-based treatment, usually used in the treatment of cancers. There are numerous, different types of chemotherapy drugs that can be prescribed by a specialist. These can commonly be used alongside other cancer treatments such as surgery and radiotherapy.

Diabetes

A metabolic disorder that is caused by problems with insulin secretion and regulation and which is characterized by high blood sugar levels. Also known as diabetes mellitus.

Types

Nongonococcal septic arthritis

This is septic arthritis that is caused by organisms other than Neisseria gonorrhoeae. A wide range of organisms can be the cause, but Staphylococcus aureus is the most common.

It is more likely to occur in older people and young children. Knees and hips are the joints most likely to be affected.

Gonococcal septic arthritis

This form of septic arthritis is caused by Neisseria gonorrhoeae, the type of bacteria responsible for the sexually-transmitted disease gonorrhea.

Initially, people with gonococcal septic arthritis tend to experience pain that shifts through the joints such as the knees, ankles, wrists and elbows. Following this:

Around 60% experience a form of inflammation called tenosynovitis (affecting the lining of tendons) that affect joints such as wrists, ankles, toes and fingers[1], and;

Around 40% experience an infection in one joint such as the knee, elbow or wrist[1].

Most people with gonococcal septic arthritis also develop lesions on the skin of their extremities, particularly the palms of the hands and soles of the feet. These lesions often feature a number of small pustules.

Bacteria

Microscopic, single-celled organisms with DNA but no definite nucleus. Bacteria are the cause of many human diseases.

Infection

Entry into the body of microorganisms that can reproduce and cause disease.

Inflammation

A body’s protective immune response to injury or infection. The accumulation of fluid, cells and proteins at the site of an infection or physical injury, resulting in swelling, heat, redness, pain and loss of function.

Joints

A connecting surface or tissue between two bones.

Lesions

Damage to bodily tissue.

Menstruation

The periodic shedding of the lining of a woman's uterus. Typically occurring about every four weeks between puberty and menopause (except during pregnancy). The menstrual period varies between individuals, but typically lasts 3-5 days.

Organisms

A form of life. It includes single-cell forms such as bacteria and more complex forms such as fungi, plants and animals.

Signs and symptoms

Symptoms of septic arthritis include pain, heat and swelling in affected joints. The skin over the joint may be red and the pain can be severe. Often, people with septic arthritis also get chills and fever, but this is not always the case.

The knee is the joint most commonly affected, but septic arthritis can also occur in the shoulder, wrist, hip and ankle and, less commonly, in other joints.

Symptoms usually develop within hours. Usually only one joint is affected, but more than one joint can be involved.

Methods for diagnosis

Tests used to diagnose septic arthritis include:

Synovial fluid analysis. A sample of fluid from the space within the joint is withdrawn by needle, a procedure known as joint aspiration, and sent for laboratory analysis to identify the organism causing the infection, and;

X-rays are generally not useful in detecting septic arthritis, but may be recommended to identify other potential causes of pain in the joint. An MRI may be recommended in cases where it is difficult to assess a joint (such as with the hip).

Where gonococcal septic arthritis is suspected, tests to identify Neisseria gonorrhoeae infection in other parts of the body (such as the urethra, rectum, cervix and pharynx) may be recommended.

Bacteria

Microscopic, single-celled organisms with DNA but no definite nucleus. Bacteria are the cause of many human diseases.

Cervix

The lower part of the uterus, leading out into the vagina.

Infection

Entry into the body of microorganisms that can reproduce and cause disease.

MRI

A type of imaging that uses a magnetic field and low-energy radio waves, instead of X-rays, to obtain images of organs.

Pharynx

The throat cavity behind the nose and mouth, above the esophagus.

Rectum

The final part of the large intestine, leading to the anus.

Synovial

Pertaining to the fluid that lubricates joints (called synovia). A joint that produces synovia is referred to as a synovial joint.

Urethra

The duct through which urine flows from the bladder to outside the body.

Types of treatment

A stay in hospital is usually required to treat septic arthritis.

Nongonococcal septic arthritis

Antibiotic treatment

High doses of antibiotics such as vancomyacin or ceftazidime are given intravenously. Treatment is usually started as soon as possible and may begin before the type of bacteria causing the infection is definitively identified.

The choice of antibiotic may depend on many factors. The antibiotic may later be changed to better target the infection once the bacteria is identified.

Once the infection has begun to improve, lower doses of antibiotics taken by mouth may be prescribed to ensure that infection clears completely from the joint.

Antifungal treatment

In the much-less common case of a fungus causing the infection, antifungal medications will be used to treat the infection.

Viral infections

Infections of joints caused by viruses generally resolve over time without treatment. Antibiotics do not help to treat viral infections.

Drainage of the joint

Pus is drained from the joint to reduce damage while the antibiotics are fighting the infection. This may need to be repeated multiple times. Depending on the joint affected, drainage may be done with a needle, an arthroscope or, particularly with hip joints, open surgery may be required.

Infection in an artificial joint

If the infection occurs in an artificial joint, the prostheses may need to be removed in order for the infection to be treated. They can usually be replaced once the infection has settled down.

Pain relief

Pain-relief medications such as non-steroidal anti-inflammatories (NSAIDs, including ibuprofen) can help to reduce symptoms such as pain, inflammation and fever.

For the first few days, the joint may be placed in a splint because any movement of the joint is often very painful. However, splinting is usually only recommended for a short time.

Physiotherapy

Physiotherapy is very important to preserve function in the affected joint. Initially, exercises that maintain the range of motion of the joint can help recovery. When the infection has subsided, more strenuous exercises to strengthen the muscles around the joint may be recommended.

Gonococcal septic arthritis

This form of arthritis usually responds quickly to antibiotics (such as azithromycin and ceftriaxone) given intravenously.

Antibiotic

Chemical substances that kill or suppress the growth of bacteria.

Arthroscope

An instrument used to view inside a joint and treat joint conditions.

Bacteria

Microscopic, single-celled organisms with DNA but no definite nucleus. Bacteria are the cause of many human diseases.

Fungus

An organism from the fungi kingdom, which is a separate group to plants or animals, and includes yeasts, molds and mushrooms. Fungi feed on organic matter.

Infection

Entry into the body of microorganisms that can reproduce and cause disease.

Inflammation

A body’s protective immune response to injury or infection. The accumulation of fluid, cells and proteins at the site of an infection or physical injury, resulting in swelling, heat, redness, pain and loss of function.

Intravenously

Within a vein.

Joints

A connecting surface or tissue between two bones.

Physiotherapy

A healthcare profession that treats bodily weaknesses or defects with physical remedies, such as massage or exercise.

Pus

A bodily fluid that is the result of an inflammatory response at an infection site. Its color can range from whitish to yellow to green, depending on the composition. Pus is mainly composed of dead bacteria, white blood cells and cellular debris.

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